Abstract TMP40: Revascularization in Patients With Moyamoya Decreases Abnormally High Posterior Circulation Arterial Flows Measured by Quantitative Magnetic Resonance Angiography

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Introduction: Moyamoya disease and syndrome are well known to affect the anterior cerebral circulation by progressive steno-occlusive disease of the supraclinoid internal carotid arteries. Less attention has been paid to changes in posterior arterial circulation hemodynamics in this condition. We sought to better understand the latter by using a relatively novel non-invasive imaging technique: quantitative magnetic resonance angiography (qMRA).

Hypothesis: We assessed the utility of qMRA to detect changes in arterial posterior arterial circulation flows before and after surgical revascularization.

Methods: Retrospective review of patients who met the following inclusion criteria: (1) diagnosis of moyamoya disease or syndrome with revascularization surgery at the Stanford University between September 2008 and March 2012; (2) preoperative and postoperative qMRA scans on record within a two-year time frame; and (3) high-quality qMRA images without motion artifact. Cerebral blood-vessel flow was quantified after non-contrast magnetic resonance imaging through the use of a commercially available software tool: non-invasive optimal vessel analysis (NOVA, VasSol, Chicago, USA).

Results: A total of 191 patients underwent 281 surgeries in this period of time. Of these, a cohort of 64 patients (78% female, mean age 38.5 years, 55% unilateral disease) had preoperative and postoperative qMRA studies. Preoperative arterial flows in the posterior circulation were markedly elevated compared to normative data. These flows significantly decreased after revascularization (94% direct STA-MCA bypass): right posterior cerebral artery 145 ml/min pre-surgery, 123 ml/min post-surgery, p=0.005; basilar artery 264 ml/min pre-surgery, 222ml/min post-surgery, p=0.0038.

Conclusion: Quantitative MRA shows that posterior circulation arterial flows are markedly increased in patients with moyamoya. After revascularization, there is an overall decrease in these flows that is significant in the basilar artery and right posterior cerebral artery. Further use of qMRA might be warranted to better understand moyamoya hemodynamics before and after surgery.